Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$104.31	9.626%	$114.3509	$114.35	$114.35	$114.40
Purchase #2	$139.64	12.730%	$157.4162	$157.42	$157.40	$157.40
Purchase #3	$102.42	6.527%	$109.105	$109.11	$109.10	$109.10
Purchase #4	$211.76	4.312%	$220.8911	$220.89	$220.90	$220.90
Purchase #5	$249.69	8.635%	$271.2507	$271.25	$271.25	$271.30
Purchase #6	$146.69	7.197%	$157.2473	$157.25	$157.25	$157.20
Purchase #7	$74.26	10.790%	$82.2727	$82.27	$82.25	$82.30
7 purchase totals =	$1,028.77		$1,112.5339	$1,112.54	$1,112.50	$1,112.60